In a manufacturing process of a semiconductor device, a fine pattern is generally formed using a photolithographic method. In the formation of the fine pattern, multiple substrates, which are referred to as transfer masks, are usually used. The transfer mask is formed by providing the fine pattern comprised of a metal thin film, etc. on a generally transparent glass substrate. The photolithographic method is also used in the manufacture of the transfer mask.
Refinement of a pattern for the semiconductor device requires the refinement of a mask pattern formed in the transfer mask as well as shortening of a wavelength of an exposure light source used in photolithography. Nowadays, the exposure light sources used in the manufacture of semiconductor devices are shifting from KrF excimer lasers (wavelength: 248 nm) to ArF excimer lasers (wavelength: 193 nm), that is, shorter wavelength light sources are increasingly used.
The known types of transfer masks include a binary mask including a light-shielding film pattern made of a chromium-based material on a conventional transparent substrate, as well as a half tone phase-shift mask. The half tone phase-shift mask comprises a phase-shift film pattern on the transparent substrate. The phase-shift film has functions for allowing transmission of light at an intensity not substantially contributing to the light exposure and for providing the light transmitted through the phase-shift film with a predetermined phase difference with respect to light traveling the same distance through air, thereby generating a so-called phase-shift effect.
Generally, in the transfer mask, a periphery region outside the region in which a transfer pattern is formed should ensure optical density (OD) not less than a predetermined value such that, upon the exposure transfer to a resist film on a semiconductor wafer using an exposure apparatus, the resist film will not be affected by the exposure light transmitted through the periphery region. Usually, in the periphery region of the transfer mask, OD is desirably 3 or more, and at least about 2.7 of OD is required. However, the phase-shift film of the half tone phase-shift mask has a function for allowing the transmission of the exposure light at a predetermined transmittance, and thus, it is difficult to ensure the optical density required for the periphery region of the transfer mask by this phase-shift film alone. Therefore, a light-shielding film (light blocking film) is laminated onto a semitransparent film having predetermined phase-shift amount and transmittance with respect to the exposure light, so that a laminated structure of the semitransparent film and light-shielding film ensures the predetermined optical density.
On the other hand, the use of a transition metal silicide-based material for the light-shielding film to increase the accuracy in formation of a fine pattern in the light-shielding film has been considered in recent years. Patent Document 1 discloses the relevant technique.
However, it has been recently ascertained that a MoSi-based (transition metal silicide-based) film, when irradiated with ArF excimer laser exposure light (ArF exposure light) for a long time, causes a phenomenon of pattern line width variation, which is also regarded as a problem in Patent Documents 2 and 3, etc. Regarding this problem, Patent Document 2 discloses that the formation of a passive film on a surface of a pattern formed of a MoSi-based film improves light fastness to the ArF exposure light (ArF light fastness), and Patent Document 3 discloses the technique to improve the ArF light fastness by providing the constitution in which a transition metal silicon-based material film such as a half tone phase-shift film has the oxygen content of 3 at % or more, and has the silicone content and transition metal content within a range satisfying a predetermined relational expression, and in which a surface oxide layer is provided on a surface layer of the transition metal silicon-based material film.